1. Field of the Invention
The present invention relates to a lens-interchangeable digital camera and a lens unit, a method of identifying characteristics of the lens unit and a method of judging deterioration of the lens unit.
2. Description of the Related Arts
Recently, there is a widespread use of digital cameras that record digital image data in a recording medium such as a built-in memory or a memory card. In such digital cameras, an image captured by an imaging device such as a CCD is converted into the digital image data. There are two types of the digital camera: one is an all-in-one type in which a taking lens is integrated with a camera body, and the other is a lens-interchangeable type in which one of various taking lenses is removably attached to the camera body.
Many of the lens-interchangeable cameras adopt existing systems for traditional silver halide cameras (see Japanese Patent Laid-Open Publication No. 8-171130). That is, they generally utilize interchangeable lenses for the silver halide cameras with little modification, and have a configuration in which a subject image is focused on an imaging device incorporated in a camera body, instead of using a silver halide photographic film, and image data is recorded in a recording medium.
However, since the imaging device becomes small and its resolving power is improved these days, a digital camera having a new system is considered rather than using the existing systems of the silver halide cameras. For example, a digital camera disclosed in Japanese Patent Laid-Open Publication No. 11-346325 has not only an interchangeable lens but also an interchangeable imaging module with imaging devices arranged therein.
As another new system for the lens-interchangeable digital cameras, it is considered that the imaging device is incorporated in the interchangeable lens. For this configuration, it is only necessary to connect the interchangeable lens to the camera body electrically without connecting them optically. Therefore, the structure can be relatively simplified.
In the lens-interchangeable digital camera, however, it is necessary to check captured images by doing a test shoot after the interchangeable lens is attached to the camera body, in order to obtain characteristics of each lens. Accordingly, it has been a problem that a user cannot know what kind of images can be obtained with the interchangeable lens, which is going to be used. Moreover, in the system in which the imaging device is incorporated in the interchangeable lens, the characteristics including resolving power of the imaging device, a range of zoom magnification and a field angle in macro capturing are different from each interchangeable lens. However, there has been no device that facilitates instant identification of these characteristics. In the digital camera described in the Japanese Patent Laid-Open Publication No. 11-346325, when the imaging module is exchanged, information relating to the imaging devices, a control program, and the like are sent to the camera body. However, the characteristics of the lens cannot be identified.
In addition, in the conventional lens-interchangeable digital camera, it is difficult to confirm performance deterioration of the imaging device even when quality of the captured image is degraded due to the performance deterioration of the imaging device with time.